What TV (make/model) is it?

Hi

It’s a 

According to the manual the TV appears to supports either the DTS codec or Dolby Digital Plus codec (with atmos) otherwise it falls back to stereo. So that’s likely the reason… You may however want to just confirm that with the Philips support desk.

See extract from the user-manual online pasted below;

(Sound) is heard when the audio or video file has DTS sound but the Home Theatre System has no DTS sound processing. You can fix this by setting the Digital out format of the TV to Stereo.

The Sonos Beam does not support the DTS or the DD+ codecs, so it looks like you ‘may’ only  be able to get stereo output from your TV with the Beam. You would probably have been better off using the Sonos Arc, rather than the Beam, as that does support DD+(Atmos)

Anyhow I suggest you check my findings and thoughts with your TV manufacturer, as suggested, as I’ve only glanced through the user-manual to answer your question and not studied it in depth.

TV User-Manual I viewed online:

https://download.p4c.philips.com/files/4/43pus7855_12/43pus7855_12_dfu_eng.pdf

I hope that assists.

Hi ya

Thanks for this, some great help. I can get Dolby 5.1 but only by manually setting it every time. Previously it worked just fine. I will get in touch with Phillips and see what they say. 

After changing settings on the TV, do you have to explicitly “Save changes” ?

No, not that I can see. I make the change to multichannel bypass and Dolby 5.1 works. I can’t remember if before I could get just multichannel to work but now it won’t let me select that as an option.

very strange it won’t save that setting. I’m wondering if it’s something to do with the latest update from Sonos? 

Maybe try the connection using the TV’s optical port instead (using the adapter you got with the Beam), just as a quick test and see if that makes any difference at all.

Ah yeh, great shout. Thanks. I will see what happens!